Machine tool brake devices of portable machine tools are already known which comprise a magnetic-field-type brake unit for braking a spindle and/or a machining tool when the magnetic-field-type brake unit is in at least one braking position and comprise a spindle immobilization unit for immobilizing the spindle when the spindle immobilization unit is in at least one immobilization position. The spindle immobilization unit can in this case be manually actuated by an operator.